550D

Magic Lantern has come a LONG way in the last few months. It now has almost all the same features as CHDK for photography (if not all), as well as tons of video and audio features not present in CHDK. Features like motion detection, focus tracking and racking, crop overlays, audio monitoring, lcd, face detect and audio-based remote triggering, lightning catching, ldr and hdr intervalometers, custom-set on-off intervals for timelapse, power management, bitrate control, auto-restart for video, exposure helpers (zebras, histograms, false color, waveforms), in-camera help screens for all functions, NEED I GO ON????

Check the link in the support section below for full feature list, downloads, tweaks, and support.

Canon EOS 550D, Digital Rebel T2i, Kiss Digital X4

There's NO CHDK 'port' or hacks available yet for the EOS 550D but finally there is a port, still in alpha stage from Magic Lantern :-) See section below...

Magic Lantern is now widely accepted as the replacement for CHDK on the 550D (and a few others, now). The Magic Lantern firmware has recently added a unified firmware for the 550D,60D,500D,50D,and 600D (With upcoming support for the 1100D).